Borane reducing resins

ABSTRACT

This invention relates to novel metal catalysts of a solid nonionic crosslinked resin having amine or phosphine borane adducts on or in which a reduced metal is precipitated, the method of producing said catalysts and their use in catalysis.

BACKGROUND OF THE INVENTION

This is a continuation-in-part of U.S. patent application Ser. No.24,928 filed Mar. 29, 1979, which in turn was a division of U.S. patentapplication Ser. No. 749,560, filed Dec. 10, 1976, both now abandoned.

It is known in the art [see M. L. Hallensleben, J. Polymer Science:Symposium No. 47, 1-9 (1974)]that linear and crosslinked copolymers of4-vinylpyridine borane, 4-vinylpyridine, and styrene can be prepared andused as polymeric reducing agents for aldehydes and ketones. It is alsoreported in the literature [see E. Cernia and F. Gasparini, J. AppliedPolymer Science, vol. 19, 917-20 (1975)]that 4-vinylpyridine boranehydride polymers rapidly decompose in aqueous solutions of strongmineral acids and can only be used as reducing agents for aldehydes andketones at or about neutral pH.

U.S. Pat. No. 3,928,293 granted Dec. 23, 1975 discloses solidcrosslinked thiohydrocarbon borane hydride polymers and their use asreducing agents for aldehydes, ketones, lactones, oxides, esters,carboxylic acids, nitriles and olefins. These borane polymers, althoughstabile at room temperature, can release borane (BH₃) under conditionsof reduced pressure or heat and are disclosed as being useful as aconvenient means of storing borane. U.S. Pat. No. 3,609,191 granted Sep.28, 1971 discloses polyethylene imine borane complexes which are stabiletoward hydrolysis at a pH as low as 5.0. These compositions are usefulas reducing agents in chemical plating baths for nickel, copper andsilver in a pH range of 5 to 8. However, these products are viscous orsolid polymers which range in water solubility from completely solubleto slightly soluble depending on the ratio of BH₃ to amino groups in thepolymer. The use of ion exchange resins to extract heavy metals fromaqueous solutions via ion exchange mechanisms is also reported in theart.

SUMMARY OF THE INVENTION

This invention relates to novel nonionic crosslinked resins containingamine or phosphine borane adducts of the formula: ##STR1## wherein Q isa group of the formula:

    --(CH.sub.2).sub.m --T--(CH.sub.2).sub.n --

wherein m and n are independently integers from 0 to 3; and T is thegroup ##STR2## and R¹ and R² are independently (a) hydrogen; (b) (C₁-C₈) optionally substituted alkyl; (c) (C₆ -C₁₂) optionally substitutedaryl; and

(d) (C₇ -C₁₂) optionally substituted aralkyl;

and Z is nitrogen or phosphorus, and their use as highly selectivereducing agents and as starting materials for the preparation of novelmetal catalysts for use in hydrogenation reactions.

The term "alkyl" as utilized in the present specification and claims ismeant to include both straight and branch chained alkyl groups which canbe optionally substituted with up to three substituents, preferably withup to two substituents, more preferably with up to one substituent,selected from the group consisting of hydroxy, mercapto, fluoro, chloro,bromo, iodo, nitro, methoxy, ethoxy, isopropoxy, amino, methylamino,dimethylamino, ethylamino, diethylamino, amido, methylamido anddimethylamido.

The term "aryl" as utilized in the present specification and claims ismeant to include aryl groups such as phenyl, naphthyl and biphenyl,which can be optionally substituted with up to three substituents,preferably with up to two substituents, more preferably with up to onesubstituent, selected from the group consisting of fluoro, chloro,bromo, iodo, nitro, methyl, ethyl, methoxy, ethoxy and trihalomethyl.

The term "aralkyl" as utilized in the present specification and claimsis meant to include such aralkyl groups as benzyl, phenethyl,phenylpropyl, naphthylmethyl and naphthylethyl which can be optionallysubstituted with up to three substituents, preferably with up to twosubstituents, more preferably with up to one substituent, selected fromthe group consisting of fluoro, chloro, bromo, iodo, nitro, methyl,ethyl, methoxy, ethoxy and trihalomethyl.

The preferred nonionic borane resins of this invention are those whereinT is the group ##STR3## Z is nitrogen; and R¹ and R² are independentlyhydrogen, (C₁ -C₈) unsubstituted alkyl, (C₆ -C₁₂) unsubstituted aryl or(C₇ -C₁₂) unsubstituted aralkyl.

The more preferred nonionic borane resins of this invention are thosewhere T is the group ##STR4## Z is nitrogen; and R¹ and R² areindependently hydrogen, (C₁ -C₄) unsubstituted alkyl or unsubstitutedphenyl, biphenyl, benzyl or phenethyl.

DETAILED DESCRIPTION OF THE INVENTION

The solid nonionic crosslinked borane reducing resins of this inventionare highly selective reducing agents which are particularly useful inselectively reducing at room temperature, from both aqueous andnon-aqueous media, mercury, silver, gold, platinum, palladium, rhodium,iridium, antimony, arsenic and bismuth ions; to the exclusion of copper,nickel, zinc, iron, lead, tin, cadmium, vanadium, chromium, uranium,thorium, cobalt, thallium, aluminum and the Group I and II members ofthe Periodic Table. These resins reduce the metal ions in solution viaelectron transfer and precipitate the reduced metals on and/or into theresin.

These borane resins are capable of being utilized over a wide range ofpH conditions and can be utilized at pH ranges greater than about 1.0but less than about 8.0. These resins are preferably utilized at pHranges of from about 2.0 l to about 4.0. These borane resins are notonly stabile in acidic and basic media but are also air stabile as well.

The solid nonionic crosslinked borane reducing resins can also beutilized as reducing agents for aldehydes, ketones, olefins and otherfunctional groups capable of undergoing hydroboration reactions. Thesereagents reduce the aldehydes, ketones, olefins and the like via hydridetransfer and the resultant product can be liberated from the resin viastrong acid hydrolysis. An added feature of this reduction procedure isthe ability of these resins to concentrate the products onto the resinthereby effecting a concentration and a purification of the productsformed before hydrolyzing them off the resin. Although themacroreticular form of the resin is preferred, the gel form or any otherparticulate form of the nonionic borane reducing resins of the presentinvention can be utilized as reducing agents.

The reduced metals which are precipitated on and/or into the nonionicborane reducing resins of the present invention can be either dissolvedout of the resin via strong acid or in the case of mercury can bewithdrawn by treatment with hot water. The more preferred method ofobtaining the reduced precious metals from the resins is by burning theresin away from the metals since the value of the precious metals farexceeds the cost of the resin.

These nonionic borane reducing resins have an advantage over ionexchange resins in that ion exchange resins have distinct leakageproblems due to the various ion exchange equilibria for each specificmetal ion and ion exchanger. There is no such leakage problem due to ionexchange equilibrium kinetics in the nonionic borane reducing resins ofthe present invention. These resins reduce the metals to their zerooxidation state and precipitate them on and/or into the resin. Anotheradvantage of these resins and in particular of the macroreticular resinsis their ability to contain large capacities of reduced metals beforebreakthrough finally occurs.

A preferred embodiment of this invention is the use of the solidnonionic crosslinked amine and phosphine borane reducing resins asstarting materials for the preparation of novel metal catalysts for usein hydrogenation reactions. The resultant metal containing resins caneither be pyrolyzed to give a carbon-metal reduction catalyst or theycan be combusted in the presence of oxygen to give the metal in a beadform. Moreover, catalysts containing known percentages of metals or ofmixed metals can be formed via this process. The nonionic boranereducing resins of the present invention can be prepared by thefollowing general synthetic routes.

In the preparation of the nonionic borane reducing resins of the presentinvention a suitable water-insoluble crosslinked resin having afunctional group of the formula ##STR5## wherein Q, R¹, R² and Z are asdefined in Formula (I) above, is reacted with a suitable protonatingmineral acid such as hydrohalic, phosphoric, sulfuric and the like,preferably hydrochloric acid to form the cationic group of the formula##STR6## This reaction is carried out in either a batch or columnprocess at temperatures from about 0 to about 100° C., preferably atabout 20° C., in a suitable protic solvent preferably water. The amountof protonating acid used can be anywhere from 5% of the equivalents ofweak base in the resin to any percentage over and above the equivalentsof weak base in the resin, but is preferably utilized in a 25% excessover the equivalents of weak base in the resin. After the protonationstep has taken place, the resin is then treated with a water wash toremove any excess acid and then washed thoroughly with a suitable dryingsolvent such as methanol, ethanol, propanol, acetone, dimethylformamideand the like or alternatively can be air or vacuum dried. In a morepreferred process for this protonation step the reaction is carried outin a batch process and a stoichiometric amount of acid is added toprotonate all the available protonizable groups. Longer reaction timesare preferred in this process since it allows complete diffusion of theacid throughout the resin beads. The borane is preferably incorporatedinto the protonated resin by treating the resin either in a column orbatch process with an excess of a solution of lithium, sodium orpotassium borohydride dissolved in an appropriate solvent such asmethanol, ethanol, dimethylformamide, monoglyme, diglyme and the like attemperatures from about 0 to about 150° C. preferably at about roomtemperature.

Another method for incorporating the borane into the resin is bydirectly treating the amine or phosphine functionality with diborane gaseither in a column or batch process or with a solution of diborane in anappropriate solvent such as diethyl ether, tetrahydrofuran, and the likeat temperatures from about 0 to about 150° C. preferably at about roomtemperature.

Those resins which contain amide functions either in the T, R¹, or R²groups can be converted into amines via the use of excess borohydridereagent, thereby reducing the bulk and increasing the ratio of theamount of borane to the amount of resin.

In the preparation where less than an equivalent of borohydride ordiborane is utilized a mixed cationic and nonionic borane reducing agentis obtained which would remove metal complex anions and metal cations byboth anionic exchange and by reduction of the metal cation or metalcomplex anion by the borane to the zero oxidation state.

Suitable crosslinked resins which can be utilized in the preparation ofthe nonionic borane reducing resins of this invention are thosedescribed in U.S. Pat. No. 2,675,359 granted Apr. 13, 1974; U.S. Pat.No. 3,037,052 granted May 29, 1962; U.S. Pat. No. 3,531,463 granted Sep.29, 1970; and U.S. Pat. No. 3,663,467 granted May 16, 1972. Theprocedures described in these patents for making the crosslinked resinsin both the gel and macroreticular form which are contained therein areall incorporated herein by reference.

The following examples are provided to illustrate the preparation of thenonionic borane reducing resins of the present invention and are not tobe considered in any way as limitations on the breadth and scopethereof.

EXAMPLE I Synthesis of the acrylic based amine-borane reducing resinStem A. Protonation

A sample (50.0 g) of an acrylic based, macroreticular, weak base resinhaving a weak base capacity of 5.4 meq. of weak base per gram of dryresin is stirred with an aqueous hydrochloric acid solution containing360 meq. of hydrochloric acid (30% excess) for 5 hours. The resin iswashed with deionized water to a neutral pH, then with two 300 mlportions of acetone and then vacuum dried at 50°C. for 8 hours. Yield,59.9 grams.

Step B. Borane Addition

To a 500 ml round bottom three neck flask equipped with a sealedmechanical stirrer, pressure compensating dropping funnel and mineraloil bubbler, is added a sample (52.8 g, 238.1 meq. of H⁺) of a driedacrylic based, macroreticular weak base resin (in the hydrochlorideform) containing 4.51 meq. of H⁺ per gram of dry resin. A solution ofsodium borohydride (10.0 g, 97% purity, 256 meq. 7% excess) in 250 ml ofdry N,N-dimethylformamide is added rapidly with continuous stirring. Themixture is stirred at room temperature until no further hydrogen gasevolution is observed. The N,N-dimethylformamide is removed byfiltration and the remaining resin is backwashed with deionized wateruntil no chloride ion is detectable with silver nitrate and the pH isapproximately seven. The resin is then vacuum dried at 30° C.

EXAMPLE II Synthesis of the Polystyrene Based Amine-borane ReducingResin Step A. Protonation

Utilizing the procedure in Example I, Step A, and a polystyrene based,macroreticular, weak base resin the desired intermediate protonatedproduct is obtained.

Step B. Borane Addition

Utilizing the procedure in Example I, Step B, and a protonatepolystyrene based, macroreticular, weak base resin, the desired boraneaddition product is obtained.

EXAMPLE III Synthesis of Polystyryl-diphenylphosphine-borane ReducingResin Step A. Preparation of polystyryl-diphenylphosphine

Utilizing the procedures in J. Org. Chem. Vol. 40, No. 11, p. 1669(1975), the macroreticular form of the polystyryl-diphenylphosphine isprepared.

Step B. Borane Addition

A sample of macroreticular polystyryl-diphenylphosphine (10.0 g., 5.0meq. phosphine/gram) is allowed to react with a tetrahydrofuran solutioncontaining diborane (100 ml, 50 meq. BH₃). The mixture is stirred atroom temperature for 3 hours. The resulting resin is washed withtetrahydrofuran and is vacuum dried.

EXAMPLE IV Iodine Determination of Borane Concentration in BoraneReducing Resins

The presence and amount of borane functionality is determined by thereaction of the resin with an aqueous iodine solution and titration ofexcess iodine with a standardized solution of sodium thiosulfate. Inthis determination it is imperative that the amount of iodine adsorbedby the resin matrix be calculated for the blank. Thus, the amount ofiodine reduced by the borane functionality is equal to the total amountof iodine removed minus the amount absorbed by the polymer. Thisadsorption blank approach is only valid for borane resins containingborane concentrations approaching the theoretical amount, i.e. all weakbase sites coordinated with borane.

EXAMPLE V Reduction of Cyclohexanone to cyclohexanol with amineboraneresin in aqueous or non-aqueous media

Samples of acrylic amine-borane and styrene based amine borane resins aswell as their weak base analogs from which they are derived are exposedto both aqueous and tetrahydrofuran solutions of cyclohexanone of knownconcentration (4%) for a period of two hours. During this time noreaction of the cyclohexanone is observed as evidenced by achromatographic determination of its original concentration. To eachsample is added an amount of acid, HCl for the aqueous system and BF₃for the tetrahydrofuran; in an amount equivalent to the concentration ofthe cyclohexanone. Both amine-borane resins revealed an immediatedecrease in the concentration of cyclohexanone. The formation ofcyclohexanol is observed in the aqueous system. However, no cyclohexanolis observed in the tetrahydrofuran solution which is to be expected inthe presence of BF₃ which would complex the alcohol. The loss ofcyclohexanone is however indicative of the reaction of the amine boraneresin with cyclohexanone.

EXAMPLE VI Batch equilibrium capacities for several precious metals

Batch equilibrium capacities are determined by reacting a known amountof amine-borane resin with an aqueous solution of the metal ion underinvestigation for a period of 16 hours with continuous shaking. Theinitial and final concentrations of the metal ion are determined byatomic absorption spectroscopy and capacities calculated from thedifference.

Samples of amine-borane resin are reacted with aqueous solutions ofAuCl₄ - PdCl₄ ⁻², and PtCl₆ ⁻² of known concentration according to theabove procedure. The results are listed in the following table.

    ______________________________________                                        Amine-borane         Initial  Final  Capacity                                 resin weight         Conc.    Conc.  g metal/                                 in grams   Metal ion grams    grams  gram                                     ______________________________________                                        0.1090     AuCl.sub.4.sup.-                                                                        0.315     0.0705                                                                              2.25                                     0.1020     PtCl.sub.6.sup.-2                                                                       0.322    0.122  1.96                                     0.1020     PdCl.sub.4.sup.-2                                                                       0.194    0.076  1.16                                     ______________________________________                                    

EXAMPLE VII Precious metal recovery by combustion

Recovery of the metal from the metal filled beads is easily accomplishedby burning the resin matrix away under an oxygen atmosphere.

A sample of gold filled resin (3.004 g) is combusted at 800° C. for 30minutes in a furnace. Bright colored metalic gold beads are recovered(1.646 g) corresponding to an initial weight percent of 55%. The beadsappear as uniform spheres possessing rough surfaces. Similar results areobtained from palladium and platinum filled resins under identicalconditions.

EXAMPLE VIII Catalyst Formations

Samples (1.00 g) of palladium or platinum filled beads are pyrolyzed at600° C. under a stream of nitrogen for 30 minutes. The resultingspherical beads appear as carbon spheres of high density attributed tothe presence of the metal.

EXAMPLE IX Metal reducing selectivity

The amine-borane resin reactivity for various metals is determined byplacing a sample (0.10 g) in a vial and adding a concentrated solutionof the metal ion or complex under investigation. The vial is allowed tostand for 3 weeks to ensure sufficient contact time. Reaction isconfirmed by either a visible change in the beads such as a darkening incolor, an increase in weight of the beads when washed with DI water andvacuum dried, or their inability to further reduce solutions of AuCl₄ ⁻.Likewise a positive reduction of AuCl₄ ⁻ indicates that no reaction withthe metal ion under investigation has occurred. The following tablerepresents those metals investigated and their ability to be reduced.

    ______________________________________                                        Metal Ion Source      Not Reduced Reduced                                     ______________________________________                                        Na.sup.+  NaCl        ×     -                                           K.sup.+   KCl         ×     -                                           Li.sup.+  LiCl        ×     -                                           Mg.sup.+2 MgCl.sub.2  ×     -                                           Ca.sup.+2 CaCl.sub.2  ×     -                                           Cr.sup.+3 CrCl.sub.3  ×     -                                           Cr.sup.+6 K.sub.2 Cr.sub.2 O.sub.6                                                                  ×     -                                           UO.sub.2.sup.+                                                                          UO.sub.2 NO.sub.3                                                                         ×     -                                           Bi.sup.+3 Bi(NO.sub.3).sub.3                                                                        -           ×                                     As.sup.+3 As.sub.2 O.sub.3                                                                          -           ×                                     Mn.sup.+2 MnCl.sub.2  ×     -                                           Fe.sup.+2 FeCl.sub.2  ×     -                                           Fe.sup.+3 FeCl.sub.3  ×     -                                           Co.sup.+2 CoCl.sub.2  ×     -                                           Ni.sup.+2 NiCl.sub.2  ×     -                                           Cu.sup.+2 CuCl.sub.2  ×     -                                           Zn.sup.+2 ZnCl.sub.2  ×     -                                           Rh.sup.+3 RhCl.sub.3  -           ×                                     Pd.sup.+2 PdCl.sub.2  -           ×                                     Ag.sup.+1 AgNO.sub. 3 -           ×                                     Cd.sup.+2 CdCl.sub.2  ×     -                                           Ir.sup.+3 IrCl.sub.3  -           ×                                     Pt.sup.+4 H.sub.2 PtCl.sub.6                                                                        -           ×                                     Au.sup.+3 HAuCl.sub.4 -           ×                                     Hg.sup.+2 HgCl.sub.2  -           ×                                     Sb.sup.+3 Sb.sub.2 O.sub.3                                                                          -           ×                                     Sr.sup.+2 SrCl.sub.2  ×     -                                           Pb.sup.+2 PbCl.sub.2  ×     -                                           Tl.sup.+1 Tl.sub.2 (SO.sub.4)                                                                       ×     -                                           Pb.sup.+4 Et.sub.4 Pb ×     -                                           CH.sub.3 Hg.sup.+                                                                       CH.sub.3 HgCl.sup.-                                                                       -           ×                                     ______________________________________                                    

EXAMPLE X Analytical determination of gold

A gold solution containing 5 ppm Au⁺³ (1000 ml) is allowed to react witha sample of the amine-borane resin in a column operation under very slowflows (0.5 ml/min). After loading is completed, the resin is assayed forgold and it was determined that a quantitative amount of gold ispresent; thus, establishing the resins utility as an analytical methodfor determining trace amounts of gold or other reactive trace metals.

EXAMPLE XI

Borane reducing resins differing in their polymeric backbones weresynthesized by the procedures disclosed in the foregoing examples. Thespecific experimental procedure utilized is illustrated as follows withone particular backbone:

A sample of macroreticular dimethylaminopropylmethacrylamide (DMAPMA)resin with a total anion exchange capacity (TAEC) of 5 meq./g isconverted to the hydrochloride form, rinsed with deionized water anddried in vacuo for 72 hours.

To a 500 ml round bottom flask equipped with a sealed mechanical stirrerand a vent to the hood, is added 47.6 g DMAPMA.HCl resin suspended in200 g dimethylformamide (DMF). The stirring mixture is charged with 9.9g sodium borohydride and is allowed to react overnight at ambienttemperature. The solvent is siphoned from the beads and the resin iswashed with deionized water. Yield: 54.9 g wet.

The amine borane resin is dried in vacuo at 55° for 72 hours.

Several borane reducing resins prepared by this general procedure aregiven in Table I below.

                  TABLE I                                                         ______________________________________                                        Resin No.   Type of Resin Backbone                                            ______________________________________                                        1           an acrylic resin (Amberlite® IRA-35                                       resin, a product of Rohm and Haas                                             Company)                                                          2           a styrene resin (Amberlite® IRA-93                                        resin, a product of Rohm and Haas                                             Company                                                           3           A dimethylaminopropylmethacrylamide                                           resin (DMAPMA)                                                    ______________________________________                                    

The borane reducing resins in Table I were loaded with platinum metal inthe zero oxidation state by the procedures disclosed in the foregoingexamples.

The following procedures are the specific procedures utilized to preparethe platinum loaded form of the borane reducing resin.

Platinum Loaded Resin A

A stock solution is prepared to contain 0.498 g K₂ PtCl₆ /100mldeionized water. Into a 100 ml stock solution (0.20 g Pt) is added 2.000g dried Resin No. 1 (TABLE I) and the resin is contacted with thesolution for two days. After this period, the supernatant is siphonedfrom the beads and the resin is treated with about 15 ml-20 ml of stockformaldehyde solution (2.3 moles formaldehyde in 1.5-liter 1N HCl) over10-72 hours. The formaldehyde treatment is used to cleave any remainingN-borane group after precipitation of the metal onto the resin, thusreducing the overall yield. The sample is washed with deionized waterand dried at 80°-90° C. overnight. Yield: 2.159 g dry.

Platinum Loaded Resin B

In like manner, a dried sample of Resin No. 1 weighing 7.005 g is addedto 105 ml of K₂ PtCl₆ stock solution. As specified above, the resin isfirst treated with the formaldehyde solution, washed, then dried. Yield:6.774 g dry.

Platinum Loaded Resin C

In like manner, a dried sample of Resin No. 2 (TABLE I) weight 2.0012 gis added to 100 ml K₂ Pt_(Cl) ₆ stock solution, then treated asspecified above.

Platinum Loaded Resin D

In like manner, a dried sample of Resin No. 2 weighing 7.0013 g is addedto 105 ml K₂ PtCl₆ stock solution, then treated as above.

Platinum Loaded Resin E

In like manner, a dried sample of Resin No. 3 (TABLE I) weighing 2.0022g is added to 100 ml K₂ PtCl₆ solution and treated as above. Yield:2.4196 g dry.

Pyrolyzed Platinum Loaded Resin F

A 3.00 g sample of platinum loaded resin D was pyrolyzed at 800° C.under 20% steam.

In order to test the resins A through F as hydrogenation catalysts, thefollowing procedure was utilized with the exception that an equivalentamount of platinum resin was utilized to replace the PtO₂ used in thisexperiment.

Test Procedure 1

A standard catalytic hydrogenation with Adams' Catalyst (PtO₂) isconducted in a Parr hydrogenation apparatus. In a 500 ml reactor bottleis charged 0.1 g Adams' Catalyst, followed by 8.4 g cyclohexene in 200ml absolute ethanol. The 4-liter tank, pressurized with hydrogen to50-60 psi, is joined to the reactor bottle via a polypropyleneconnecting tube inserted through a stopper. The reactor bottle, sheathedwith a guard screen, is stoppered, then set into the bottle holder. Airis evacuated from the reactor to a negative pressure and replaced withhydrogen gas to 40 psi. The pressure on the main tank is noted, theshaker is started and a pressure drop in the reactor is observed. Whenthe pressure in the bottle reaches 10-15 psi, the reactor is filled withhydrogen to 40 psi. The pressure drop in the hydrogen tank is noted.This is repeated until there is no observed pressure drop in thereactor. For Adams' Catalyst, the total observed pressure drop in thehydrogen tank is 9.5 psi in 48 minutes.

Test Procedure 2

In like manner, the sample identified above as Platinum Loaded Resin Ais tested for catalytic activity as described in Test Procedure 1. Thetotal pressure drop is 9.1 psi in 71 minutes.

Test Procedure 3

In like manner, 2.58 g of the sample identified above as Platinum LoadedResin B is tested for catalytic activity as specified in TestProcedure 1. The total pressure drop is 7.5 psi in 107 minutes.

Test Procedure 4

In like manner, the sample identified above as Platinum Loaded Resin Cis tested for catalytic activity as described above. The total drop is10.2 psi in 40 minutes.

Test Procedure 5

In like manner, the sample identified above as Platinum Loaded Resin Eis tested for catalytic activity. The observed pressure drop is 10.5 psiin 117 minutes.

Test Procedure 6

The pyrolyzed resin, Resin F, is tested for catalytic activity in themanner described above. The pressure drop is 9.1 psi in 53 minutes.

Table II below summarizes the results of the above tests.

                  TABLE II                                                        ______________________________________                                                    Hydrogenation of Cyclohexene                                                                     (0.1 mole)                                     Resin ID & % Pt*                                                                          H.sub.2 Pressure Drop (psig)                                                                     Time (min)                                     ______________________________________                                        Adams' Catalyst                                                                           9.5                48                                             (PtO.sub.2)                                                                   Resin A (10% Pt)                                                                          9.1                71                                             Resin B (3% Pt)                                                                           7.5                107                                            Resin C (10% Pt)                                                                          10.2               40                                             Resin E (10% Pt)                                                                          10.5               117                                            Resin F (3% Pt)**                                                                         9.1                53                                             ______________________________________                                         *Percentage by weight Pt based on weight of resin substrate.                  **Resin F is pyrolyzed version of Resin D (omitted from test).           

To illustrate the suitability of various other aliphatic and aromaticcopolymer backbones for preparing the amine or phosphine borane adductsof the present invention, the following experiments are conducted:

EXAMPLE XII

A sulfonamide amine weak base macroreticular resin is prepared inaccordance with the teachings of U.S. Pat. No. 4,217,421.

The resin backbone copolymer is prepared by aqueous suspensionpolymerization of a monomer mixture of 97 parts styrene, 3 partsdivinylbenzene (commercial grade=55% DVB, remainder≅EVB). The copolymeris isolated, chlorosulfonated and amidated with1,1,9,9-tetramethyliminobispropylamine to yield a weak base anionexchange resin. This resin is then converted to the HCl form (columntreated with 4% HCl and rinsed with DI water) and dried in vacuo for 72hours.

The dry resin is suspended in 42 g DMF and 2.08 g NaBH₄ is added to thereaction mixture. After stirring overnight, DMF is siphoned from themixture and the beads are washed three times with deionized water (1hour each wash), then Buchner dried and bottled.

The sulfonamide amine borane resin thus prepared is tested for reducingpower by adding 0.1 g of resin to 50 ml of a 1,000 ppm Au⁺³ (AuCl₃)solution. If the resin is active to reduce the gold ion, the resindarkens within 10 minutes and the yellow-gold solution becomes colorlessupon standing overnight. The sulfonamide amine borane resin is highlyeffective in reducing gold ion by this test.

EXAMPLE XIII

A mixed macroreticular/gel resin, denominated for convenience as a"hybrid" amphoteric ion exchange resin, is prepared in accordance withthe teachings of U.S. Pat. No. 3,991,017, issued Nov. 9, 1976. The resinbackbone copolymers are aliphatic and aromatic, the former being acylicacid (10% divinylbenzene crosslinker), and the latter vinylbenzylamine(1% DVB). A borane adduct is formed at the weak base functional sites ofthe hybrid resin by the method described above in Example XII. Whentested for gold ion reduction by the method of Example XII, the hybridresin borane adduct is found to be highly effective.

EXAMPLE XIV

A macroreticular weakly basic resin is produced by known aqueoussuspension techniques from adimethylaminopropylmethacrylamide/divinylbenzene (4%) monomer mixture.This is the same resin as described above as Resin No. 3 in Example XI.After the borane adduct is formed, the resin is found to be highlyeffective for reducing gold ions from a solution according to the methoddescribed above in Example XII.

The foregoing examples illustrate the fact that a borane adductaccording to the present invention can be formed readily at any weaklybasic functional site of an ion exchange resin regardless of thebackbone copolymer composition or the presence of other functional ionexchange groups, even acidic groups (see Example XIII, above). Thebackbone copolymer merely serves as a highly inert carrier, allowing theexchange group to be fixed to a solid having good hydraulic andmechanical characteristics suitable for use in column operations.

It is well-known in the art that ion exchange copolymers containing avariety of "carbon-fixing moieties" such as sulfonate, carboxyl, amine,halogen, oxygen, sulfonate salts, carboxylate salts and quaternary aminesalts may be pyrolyzed or partially pyrolyzed in an inert atmosphere toyield a carbonaceous particle substantially free of volatile componentsand having a carbon/hydrogen ratio of about 1.5:1 to about 20:1 (seeU.S. Pat. No. 4,040,990). As used herein, the term "pyrolyzed" or"pyrolyzing" refers to the known prior art technique described in U.S.Pat. No. 4,040,990. The term "combusting" as used herein is intended torefer to the complete or essentially complete oxidation of the backbonecopolymer, including the carbon, to leave essentially only the catalyticmetal.

The non-ionic borane reducing resins of this invention can be utilizedin either batch or column operations and in addition to their use asreducing agents for metals, aldehydes, ketones and olefins, can also beutilized as an analytical reagent. These resins can be used to detectmicroquantities of metal ions in various aqueous and non-aqueous mediadue to their ability to quantitatively convert the metal ions to theirzero oxidation state and concentrate the metal on and/or into the resin.The amount of metal present in the resultant metal containing resin canthen be determined via gravimetric, spectroscopic or other analyticalmethod and the microquantities of metal in the original volume ofaqueous or non-aqueous media so treated can then be determined.

The ability of these resins to reduce ionic mercury salts and compoundsand in particular methylmercury makes them especially useful in thedetoxification of mercury polluted effluents.

Another area of application of the non-ionic borane reducing resins ofthe present invention is their used in the sugar refining industry as adecolorizing agent. In similar fashion, these resins can be utilized asreducing agents for the removal of oxide impurities in chemicals such asalcohols, glycols, amines, amides and the like.

These reducing resins can also be utilized for reducing peroxides inperoxide forming organic compounds especially in ethers such asdiethylether, tetrahydrofuran, diisopropyl ether and the like. Theseresins can be utilized in the removal of peroxides in ethers alreadycontaminated with peroxides as well as being utilized as peroxideinhibitors in the storage or use of peroxide forming compounds.

The resins of this invention when impregnated with metals such assilver, copper, mercury, etc. can be employed in industrial applicationsas microbiocides in the textiles, paint, paper and laundry industries.These same resins can also find application in the removal of traceamounts of hydrogen sulfide, sulfur dioxide and the like from naturalgas streams, coal gasification streams, coal and oil burning utilityplants, sulfuric acid plants and the like. In these latter applicationsthe potential high surface area of the finely divided, supported metalprovides a high capacity material. The non-ionic borane reducing resinscan also be utilized in elemental halogen and alkyl halide removal fromaqueous and non-aqueous media via reduction to halide ion and an alkanerespectively.

Certain of the non-ionic amine-borane reducing resins of this inventionhave applicability in organic synthesis procedures since theborane-resin adduct provides the desirable features that the reducingsupport is easily removed from the reaction mixture, the reducedmaterial is attached to the resin system providing for completeseparation of the product from the starting material. The reducedmaterial can then be recovered from the resin by acid or base hydrolysisproviding a pure product. The reducing support can then be chemicallyregenerated to the starting non-ionic amine borane reducing resin byprocedures outlined above.

Another advantage of the borane reducing resins of this invention istheir ability to provide a source of borane without the hazardsassociated with the use of this reagent. Another application for theamine-borane resins of the present invention is their use in thepetroleum industry. Petroleum refining plants utilize noble metals ascatalysts. These metals are presently recovered by dissolving them inaqua regia and then chemically reducing the metal chloride salts.However, the effluent from this process still contains about 10 to 15ppm of metal ion. Anion exchange resins are presently used to removethese final trace amounts of metal. However, rhodium salts are notefficiently removed by anion exchange resins. Thus, the use of the highcapacity amine-borane resins of the present invention can be used inplace of the anion exchange resins in the above recovery process. Thenonionic crosslinked resins containing amine or phosphine borane adductscan be advantageously employed in numerous applications as disclosedabove. Other applicatiions of these adducts which readily suggestthemselves to those skilled in the art are meant to be included withinthe scope of the present specification and claims.

In the reduction reactions disclosed herein the borane group is oxidizedforming boric acid when the oxidation/reduction is conducted in aqueousmedia. Because the borane group has the potential for losing sixelectrons in an aqueous media, it is capable of reducing six monovalentmetal ions, accounting for the high capacity of the resins of theinvention. In nonaqueous media, such as an organic media or a gas, themechanism for reduction involves hydride transfer, as mentioned above,and the borane compound found may or may not be soluble in the media. Inany event, hydride transfer involves loss of only three hydride ions bythe borane group.

I claim:
 1. A process for the preparation of hydrogenation catalystswhich comprises contacting a platinum, palladium, rhodium or iridiumcontaining aqueous or nonaqueous medium with a nonionic borane reducingresin which comprises a solid, crosslinked copolymer carbon backboneresin having a plurality of amine- or phosphine-borane adducts attachedthereto, and separating the resultant metal-containg resin.
 2. A processaccording to claim 1 which contains the additional step of pyrolyzingthe metal resin.
 3. A process according to claim 1 which contains theadditional step of combusting the metal containing resin in the presenceof oxygen.